N = int(input())
A = list(map(int, input().split()))


def f(x):
    # 全部の要素をx以下にできるか
    for i in range(31, -1, -1):
        b = 0
        for a in A:
            if (a >> i) & 1:
                b |= 1
            else:
                b |= 2
        if b != 3 and (x >> i) & 1:
            return True
        if b == 3 and not (x >> i) & 1:
            return False
    return True


l, r = -1, 10**9 + 1
while r - l > 1:
    m = (l + r) // 2
    if f(m):
        r = m
    else:
        l = m
print(r)